Strong Localization of the Density of Power Losses in Type-II Superconducting Wires

A round straight superconducting wire has been used as numerical prototype for pursuing a comprehensive study on the local distribution of current and the density of power losses, attained by the simultaneous action of an ac transport current and an oscillating transverse magnetic field. The numerical simulations have been performed within the quasi-steady approach of the critical state theory, including virgin and premagnetized wires. A wide variety of shapes for the flux fronts characterizing the local dynamics of the electromagnetic quantities across the section of the wire has been revealed. Under special conditions, flux fronts characterized either by the so-called “field-like”, or “current-like ” shapes are shown, with the occurrence of multiple domains of current flow detached by thin lines acting as boundaries between the critical values Ic and -Ic. Despite the lack of symmetry for attaining at least an intuitive definition of the shape of the flux front, a universal pattern of the distribution of magnetic flux density has been identified. Also, a strong asymmetric localization of the density of power losses has been envisaged, as long as synchronous electromagnetic excitations are used.